Concentration of latex



of the usual stabilizing agents added to the latex,

Patented June 6, 1939 i a 2 161 455 UNIEED'TSTA'ITE'S. #PATEN T io FxFlCE.

CONCENTRATION OF LATEX Albert M. Clifford, Stow, Ohio, assignor to Wing- Ioot Corporation, Wilmington, DeL, a corporation ofDelaware No Drawing. Application October 31, v1935,

. Serial No. 47,728

Claims. (CI. 1850) This invention relates to the concentration and by heating in an open vessel with stirring over stabilization of latex. It includes the process of a water bath at a temperature of IO-80 C. Afconcentration and the concentrated product. It ter one hour the concentration of rubber was also includes stabilized latices. Furthermore it increased to 42.5%. After 1.5 hours it was in- 5 includes as new compounds the alkali metal salts creased to 48.2%. The concentration was ef- 5 of lauryl phosphate, such as the sodium and fected smoothly with no more than slight tendpotassium salts. ency to skin formation over the outer portions It has been found that the alkali metal salts of the vessel which were not thoroughly agitated. of the phosphoric esters of higher alcohols are The concentrated latex was redispersible. It was useful as stabilizers for rubber latices. They obtained in the form of a smooth soft paste. 10 may be used for stabilizing unconcentratei latex Microscopic examinations showed the 48% paste and also for stabilizing latices concentrated by to be completely redispersible in water but no various different methods. When added to latex different in appearance from the 32.4% concenduring concentration these salts prevent the tration. There was no coagulum and no aggre- 5 latex from coagulating under conditions which gation of particles. 5

would otherwise cause coagulation.

The latex to be concentrated may be fresh Example 2 latex or preserved latex but preferably is latex which is stabilized by the addition 01' some one 3 1? $35 121? 2 5 5 8: 235;?

with absolute ether for 24 hours. The ether was decanted and evaporated at room temperature.

This gave 49.7 parts of viscous liquid which by titration was found to contain 79.70% monolauryl phosphate. One part by weight of mono-.

lauryl phosphate was suspended -in 50 parts of 25 water and made alkaline to phenolphthalein by the addition of dilute sodium hydroxide. This and sufficient water were added to 150 grams of concentrated latex (containing 60% rubber and which agent, however, does not prevent coagulation of latex when it is evaporated. Agents ordinarily employed for this purpose include ammonia, formaldehyde, sodium sulflte, etc. In- 25 stead of using latex of normal rubber concentration, i. e., as it comes from the tree, the latex may first be concentrated to some extent by any other known method such as by centrifuging or creaming and then if an alkaline salt of one of l the phosphoric esters of a higher alcohol is added 30 the latex may be further concentrated by evap- Egg; :3 :3 $3 3 gggi ggfi g ggfi oration Wlthout undesirable The The resulting mixture was concentrated by heatconcentrated product produced in any of these mg on a Water bath at 80 90 C- The original Ways product of high .mbber cgntent and mixture contained 32.5 parts of rubber. After .contams s0me of the alkali metal salt of the 1% hours heating ambber content of 545% was 35 phosphoric. acid ester of the higher alcohol obtained and after two hours a concentrated ployed during the concentration by evaporation. latex of 625% rubber content was obtained.

, Example 1 h h t Example 3 40 A solution of sodium monocetyl p osp a e was 40 prepared by adding a small amount of water to SIX hundred of fresh ex 3% dry 5.0 parts by weight of monocetyl phosphate folbe co tent) Conta 3% NH: were treatlowed by the gradual addition of NaOH with ed with 35 grams of Sodium y p p a e "shaking until the ester had dissolved and the a evaporated at wlth constant stirsolution was slightly alkaline to phenolphthalein. on a Water bath will the final concentra- 45 The total amount of the solution was 173 parts non was 584% dry f contemby weight Other salts of phosphoric esters of higher alco- To 170 parts by t; of a concentrated latex hols which may be employed for the stabilization containing approximately 60% of rubber d of unconcentrated and concentrated latices and ammonia only, as a stabilizing agent, 160 parts which prevent the a ula Of lateX On p- 50 by weight of the above prepared sodium cetyl oration include esters of primary alcohols conphosphate ti was added, The resulting taining 10 to 30 carbon atoms such as the alkali mixture was stirred until homogeneous and a m l Salts f ph p r c esters of ceryl, octasample withdrawn showed a rubber concentradecyl, melissyl and myricyl alcohols. tion of 32.4%. This mixture was evaporated The preparation of the sodium salt of lauryl 55 phosphate is given in Example 2. Other salts such as the potassium salt may be made by using potassium hydroxide instead of sodium hydroxide as there described.

I claim:

1. The method of concentrating latex by evaporation which comprises heating latex to which a di-alkali metal salt of a phosphoric acid ester of a comprises heating latex which contains a dialkali metal lauryl phosphate.

4. The method of concentrating latex which comprises heating latex which contains an alkaline alkali metal salt of a higher aliphatic alcohol phosphate.

5. The method of concentrating latex which comprises adding an alkaline alkali metal salt of a phosphoric acid ester of a higher aliphatic primary alcohol to a concentrated latex and then further concentrating the resulting solution by evaporation.

ALBERT M. CLIFFORD. 

